Two-phase disk contactor



l, @966 F, G, GRn/|55 ETAL 3,266,785

TWO'PHASE DISK CONTACTOR Filed Nov. 22, 1963 OX Gf/V )ad MKM UnitedStates Patent 3,266,786 TWG-PHASE DESK CNTACTR Patrick G. Grimes,Milwaukee, and Marvin C. Raetlier,

lirookiieid, Wis., turing Company, Milwaukee, Wis.

Filed Nov. 22, 1963, Ser. No. 325,592 2 Claims. (Cl. 261-92) Thisinvention relates generally to two-phase contactors. More specifically,this invention relates to disks used in two-phase contactors.

The two-phase contactor generally utilizes a plurality of elements whichare dipped into a liquid, exposed to gas and then returned into theliquid. This device is also applicable when two immiscible liquids areused. The twophase contactor is used as a means to selectively absorbinto or remove from a fluid certain elements or gases. Examples ofsuccessful applications of this type of a device are: removing dustparticles from an air stream and oxygenating liquids.

Two-phase contactors frequently utilize a plurality of disks which arerotated into a liquid and then exposed to a gas. As they are beingrotated, the surface of the disks picks up a thin film of liquid. Thesedisks usually rotate slowly to avoid throwing the liquid film olf thedisk by centrifugal force. As a result, the surface of the liquid filmis usually saturated with the gas passing over the exposed portion ofthe disk within a very short time after the hlm emerges from the liquid.It has been recognized that a greater amount of gas can be absorbed inthe film on these disks if the amount of liquid retained on the disksand exposed to the gas is increased.

It has been suggested `that roughing the surface of the disk wouldprovide a large surface area to which the liquid would adhere andthereby expose a greater surface Y area of liquid to the gas so as toabsorb more of the gas. While this is true, roughing the surface of thedisks has proved relatively inefhcient.

This invention concerns a unique way of exposing7 a greater amount ofliquid film to the gas so as to absorb a greater volume of gas andthereby improve the efficiency of the two-phase contactor. The liquidfilm on the disk tends to liow along the surface of the disk as it isrotating. It is believed that if the flow path of the liquid film on thedisk is elongated, a greater area of liquid film surface will be exposedto the gas and a greater volume of gas will be absorbed into the liquidbeing treated.

Generally, there are -two forms of fiow which can occur on the film. Thefirst being the laminar flow in which the top surface of the liquidflows faster than the lower layers and hence exposes the second or lowerlayer of film to the gas phase. The other form being a turbulent tiowwhere there is a type of rolling of the lilm of liquid as it tio'ws offof the contactor. This also exposes more surface of the film to the gasphase. Hence, elongating the flow distance with either type of fiow willincrease the tilm surface exposed to the gas phase.

To elongate the iiow of liquid on the disk, the diskv of this inventionhas a plurality of projections which are arranged on the flat surface ofthe disk to be in a generally horizontal position as they emerge fromthe liquid to be treated to lif-t a greater amount of liquid on the diskthan would be lifted by mere film adhering to the disk surface. Duringthe rotation of the disk, the projections assume a vertical position soas to cause the liquid to flow along the disk surface due togravitational force.

Therefore it is the object of this invention to provide a new andimproved two-phase contactor.

Another object of this invention is to provide a new and improved diskfor use in a twophase contactor.

assignors to Allis-Chalmers Manufac- Another object of this invention isto provide a disk for use in a two-phase contactor that elongates theflow of liquid on the disk.

Another object of `this invention is to provide a new and improvedtwo-phase contactor which increases the volume of gas absorbed in theliquid film on the surface of the two-phase contactor disk.

Other objects and advantages of this invention will be lapparent fromthe following description when read in connection with the accompanyingdrawings, in which:

FIG. 1 is an isometric view of a two-phase contacter having disks ofthis invention;

FIG. 2 is a front View of a disk showing the preferred embodiment ofthis invention;

FIG. 3 is an end View of the disk of FIG. 2;

FIG. 4 is a front view of a disk showing an alternate embodiment of thisinvention;

FIG. 5 is a partial section view of the disk of FIG. 4 taken along linesV-V;

FIG. 6 is a front view of a disk showing still another embodiment ofthis invention;

FIG. 7 is an end View of the disk of FIG. 6; and

FIG. 8 is a partial cross section View of a disk showing a modified formof a projection used on a disk of this invention.

Referring more specifically to the drawing by characters of reference,the two-phase contactor 10 of this invention is illustrated as a liquidgas contactor having a tank 11 with bulk liquid 12 to be -treated owingin the lower portion of the tank. A horizontally disposed shaft 13 isrotatably mounted in a pair of spaced apart bearings 14 and a pluralityof disks 16 are mounted on the shaft 13 for rotation therewith in asubstantially vertical plane. About one-half of each disk is submergedin the bulk liquid 12 to obtain maximum results. A suitable source ofpower such as the illustrated electric motor 18 is provided for rotatingthe shaft. Preferably the shaft is rotated at a relatively slow speed toavoid throwing liquid off of the disks by centrifugal force.

As the disks are rotated through the bulk liquid to be treated, a filmof liquid adheres to the surface of the disks and is carried through andis exposed to the gas phase of the contactor. As the portion of the diskout of the water is being rotated, the liquid film on the surface tendsto flow downward slightly due to gravitational force. Naturally theamount of flow depends on the thickness of the film and its naturaladherence to the material which forms the surface of the disk. If theamount of liquid picked up on the disk exceeds that amount which wouldnaturally adhere to the disk surface through surface tension, the excessportion of that liquid flows downward along the surface of the disk moreeasily than the film adhering to the disk. Since flow on the disksurface is desired in this invention, an attempt is made to lift as muchliquid as possible on the disk. Also, the speed of the disk has to bekept slow enough so that the gravitational force will overcome anytendency of centrifugal force o-f the disk to throw this liquid radiallyoutward or to neutralize it so that the liquid does not ow at all.

It hasbeen found by experimentation that the surface area exposed to thegas in this type of contactor is saturated with the gas within a veryshort time after the disk emerges from the bulk liquid. Hence, toincrease the amount of gas absorbed in the liquid a larger surface areamust be exposed to the gas.

As the liquid film on the surface of the disk tiows along the disk, itexposes additional film surface to the gas phase and more gas isabsorbed into the liquid. This is a continuing process and hence thegreater distance the film flows on the disk before re-entering theliquid in the tank,

the greater the amount of surface exposed to the gas and the greater theamount of gas absorbed in the liquid.

As mentioned above, there are basically two types of flow which occur inthis film which cover the surface of the disk. One is what is known asthe laminar flow in which the outer surfaces of theliquid flow downwardat a faster rate than the inner layers of liquid which have a greateradhesion to the surface of the disk. The other type of flow is calledthe turbulent flow in which the liquid tumbles down the surface of thedisk and as it tumbles and rolls it exposes previously submerged surfaceareas to the gas. In the contactor such as illustrated in the drawingboth types of flow occur. For example, some of the liquid tends tocascade over the ribs or projections and cause a turbulent type of flow,whereas some of the fluid tends to llow along the surface of the disk inthe trough formed between adjacent projections. In this case a laminartype flow occurs. In either case though, new unsaturated film surface isbeing constantly developed for exposure to the gas and more gas iscorrespondingly absorbed into the film.

The disk 16 illustrated in FIGS. l and 2 is the preferred embodiment ofthis invention. The disk 16 has a plurality of arcuately spacedoutwardly extending projections 21 mounted on the surface thereof.Adjacent projections form troughs 22 therebetween. These projections 21extend generally toward the center of the disk and are specificallyarranged so that when a projection 21 emerges from the bulk liquid inthe tank 11, it is in a substantially horizontal position so as toentrap on the disk a greater amount of liquid than would normally adhereto the surface of the disk by surface tension alone. As the disk 16continues to rotate, these projections 21 gradually assume and passthrough a substantially vertical position. As the projection is rotatingtoward the vertical position, gravitational forces tend to draw theliquid downward through the trough 22 between projections 21 toward thecenter of the disk. This type of llow is laminar. However, some of theliquid in the disk 16 cascades over the projections 21 thereby causing aturbulent flow. As the projection 21 assumes a vertical position, all ofthe liquid adjacent the projection is flowing downward in laminar flow.As the projection passes the vertical midpoint, any liquid which has-not flowed all the way to the center of the disk and back to the bulkliquid starts to flow across the trough 22 to the projection 21 on theother side of the trough. As the projection rotates further to near ahorizontal position just prior to re-entry into the bulk liquid in thetank 11, the liquid on the disk tends to ride up slightly on theprojection. Other of the liquid on the disk still flows toward thecenter of the disk. The net effect is to elongate the flow path of theliquid on the disk and cause it to remain on the disk for a longerperiod of time continually exposing new unsaturated film surfaces andthus more and more of the liquid to the gas. Hence, more gas is absorbedinto the film and returned to the bulk liquid in the tank.

The size and shape of the troughs or projections on the disk may bevaried to accommodate various types of liquids and materials of thedisk. Furthermore, the shape of the specific projections can bedifferent such as the example illustrated in FIG. 8 in which theprojection 25 on disk 26 is designed to have an inclined leading surface27 extending downward from the outer part of the projection toward thesurface of the disk at an angle o less than 90 so as to form a somewhatof a V-shaped trough 28 to entrap more liquid between the projection andsurface of the disk as the disk is being rotated upward through the bulkliquid. This provides a greater amount of liquid to be treated by thegas. Furthermore, the trailing surface 29 of the projection 25 can beinclined in the same direction to Iform an obtuse angle with the disksurface as compared with the acute angle formed between the disk surfaceand the leading surface 27. This configuration induces turbulent orcascading flow over the projection 25 as it moves downward from itsvertical position toward the bulk liquid.

FIGS. 4 and 5 illustrate a modified disk 32 of this invention in whichthe troughs 33 between projections 34 all terminate in groove 3S formed`by an annular projection 36 spaced radially outward from the center ofthe disk and radially inward from the ends of the projections 34. Thisparticular arrangement is intended to prevent as much as possible liquidflowing off the disk into the bulk liquid before the disk has passedentirely through the gas phase. A further modification of that type of adisk is illustrated in FIGS. 6 and 7 in which a number of cordlikebridging members 40 are positioned on disk 41 between adjacent radialprojections 42 to form pockets 44. This further retards the flow ofliquid in a radial inward direction and causes the liquid to flow downone projection across the cordlike member and then over a secondprojection 42. This construction also induces more turbulent type flow.

Experiments using the disks of this invention as cornpared with a plaindisk with a roughed surface show that the amount of oxygen absorbed inthe liquid film on the disk and hence dissolved into the bulk liquid ina given length of time can be increased by as much as 50 percent.

In operation, the liquid such as water to be treated flows through thetank 11 by means of the inlet and outlet pipes. If a gas such asatmosphere is used, it is not necessary to enclose the disks. However,if a gas other than atmosphere is to be used, the contacter should beenclosed as by tank 11 and the gas, for example oxygen, injected intothe enclosure by suitable means. During operation the disks 16 arerotated slowly with preferably 40 to 60 percent of their surface in theliquid. As one of the projections 21 emerges from the bulk liquid 12, itis in a substantially horizontal position and traps liquid between theprojection 21 and the surface of the disk in an amount which exceedsthat which would naturally adhere to the disk by surface tension alone.As the disk continues to rotate, the projection 21 gradually assumes avertical position. During this time, some of the liquid on the disk isflowing radially inward along the projection and other of the liquid iscascading over the projection. When the projection 21 is in the verticalposition, all of the gravitational force is downward and all the liquidtends to flow downward in the trough between adjacent projections. Asthe projection passes through the vertical position into the nextquadrant the liquid on the disk tends to flow across the bottom of thetrough 22 to the next projection. By the time the projection is about tore-enter the bulk liquid, it is again approaching a substantiallyhorizontal position and the liquid from the trough 22 is tending to flowover the projection 21 again toward the bulk liquid. Thus, the flow of amolecule of water could be described as being picked up betweenprojections, flowing radially inward along the project1on across thebottom of the trough, and then down the adjacent projection againradially inward toward the center of the disk and possibly flowing overa projection. By comparison, if there were no projections the liquidwould tend to flow directly to the bulk liquid immediately upon emergingfrom the liquid and would find the shortest path to the liquid. As waspointed out above, the increased path of travel of the liquid causes agreater surface area of liquid film to be exposed to the gas resultingin a much higher volume of gas absorbed in the liquid film and returnedto the bulk liquid being treated.

Although the operation was explained in detail in relation to the disk16 of FIGS. 1 and 2, the operation in connection with the otherillustrated disks would be substantially the same. This is also true ifthe phases were two immiscible liquids rather than the liquid-airillustrated.

Although only a few embodiments of this invention have been illustratedand described, it will be apparent to those skilled in the art thatvarious modications and changes can be made therein without departingfrom the spirit of the invention or scope of the appended claims.

Having now particularly descri'bed and ascertained the nature of oursaid invention and the manner in which it is to be performed, we declarethat what we claim is:

1. A two-phase contactor comprising a plurality of disks mounted `forrotation, said disks being located so as to `be partially submerged in aliquid to be treated, at least one surface of each of said disks havinga plurality of arcuately spaced inwardly extending radial projectionsformed thereon, adjacent radial projections cooperating with theintermediate disk surface to form llow contr-0l troughs therebetween,said troughs terminating in a groove formed by an annular projectionspaced radially outward from the center of the disk and radially inwardfrom the inner ends of the radial projections, said projections beingarranged to entrap liquid in said troughs upon emerging from said liquidand direct the flow of said liquid in an elongated path along thesurface of said disk as said disk is being rotated.

2. A two-phase contactor comprising a plurality of disks mounted forrotation, said disks being located so as to be partially submerged in aliquid to be treated, at

References Cited by the Examiner UNITED STATES PATENTS 844,466 2/1907Prott 261-84 X 1,619,286 3/1927 Burks 103-96 2,698,287 12/1954 Bowden etal 202-175 X FOREIGN PATENTS 21,708 1891 Great Britain.

HARRY B. THORNTON, Primary Examiner.

E. H. RENNER, Assistant Examiner.

1. A TWO-PHASE CONTACTOR COMPRISING A PLURALITY OF DISKS MOUNTED FORROTATION, SAID DISKS BEING LOCATED SO AS TO BE PARTIALLY SUBMERGED IN ALIQUID TO BE TREATED, AT LEAST ONE SURFACE OF EACH OF SAID DISKS HAVINGA PLURALITY OF ARCUATELY SPACED INWARDLY EXTENDING RADIAL PROJECTIONSFORMED THEREON, ADJACENT RADIAL PROJECTIONS COOPERATING WITH THEINTERMEDIATE DISK SURFACE TO FORM FLOW CONTROL TROUGHS THEREBETWEEN,SAID TROUGHS TERMINATING IN A GROOVE FORMED BY AN ANNULAR PROJECTIONSPACED RADIALLY OUTWARD FROM THE CENTER OF THE DISK AND RADIALLY INWARDFROM THE INNER ENDS OF THE RADIAL PROJECTIONS, SAID PROJECTIONS BEINGARRANGED TO ENTRAP LIQUID IN SAID TROUGHS UPON EMERGING FROM SAID LIQUIDAND DIRECT THE FLOW OF SAID LIQUID IN AN ELONGATED PATH ALONG THESURFACE OF SAID DISK AS SAID DISK IS BEING ROTATED.